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Does anyone know the current thinking regarding the variations in Polaris? I seem to remember reading not so long ago that it's amplitude had been declining for something like 50 years, and that perhaps it had now ceased to be a Cepheid altogether!
A couple of students at Birmingham University are desperate for information on Polaris, so I would be grateful if someone could help out.
Thanks in advance,
Gary Poyner
Dear Dr. Poyner and VSNET members;
I will send information on the variations in Polaris. I'm sorry for my rate reply and the incompleteness of information which you will find in the latter half of this post. Although somebody already have sent information, which may be more complete than this post, by a private mail, I have received no reply via VSNET till now. I hope this post has some useful information for Dr. Poyner and other VSNET members, who are interested in Polaris.
Gary Poyner wrote:
> Does anyone know the current thinking regarding the variations > in Polaris? I seem to remember reading not so long ago that > it's amplitude had been declining for something like 50 years, > and that perhaps it had now ceased to be a Cepheid altogether!
1. The paper Dr. Poyner have read may be
"Goodby to Polaris the Cepheid" by J.D. Fernie K.W. Kamper, and S. Seager, which appeared in ApJ vol. 416, No.2, 820-824 (1993).
The authors have pointed out that the pulsatinal amplitude of Polaris seems to be declining exponentially, and Polaris may be leaving from the Cepheid instability strip.
I have found other authors also reporting the similar result, however, unfortunately, I have no chance to read it.
2. In more recent literature, the other authors re-analyzed the variations of Polaris and reported that *pulsating amplitude of Polaris seems to be declining not so dramatically*. They concluded that Polaris is not at the red edge, but still in the Cepheid strip.
I'm sure that I have read above result, however, I'm not sure on name of the author and where I have found this result. I have tried to search it in some references in indexes of some of the main journals, but I have no clue for it. It may be appeared in a proceedings of a conference. This is the incompleteness I have wrote at the top of this post.
> A couple of students at Birmingham University are desperate > for information on Polaris, so I would be grateful if someone > could help out.
As you might know, the observational constraints on the red edge of the Cepheid strip brings us a fruitful information on the stellar interior. I would like to suggest to the observers who are interested in the variations of Polaris that more observations are needed to clearify whether this interesting small amplitude Cepheid, Polaris, is really leaving the Cepheid strip or not.
Best regards,
-- % Toshihito ISHIDA, Ph. D., Astrophysicist % % Nishi-Harima Astronomical Observatory, Sayo-cho, Hyogo 679-53, JAPAN % % Tel: +81-790-82-3886 ext. 142 Telefax: +81-790-82-3514 % % e-mail: ishida@nhao.go.jp (usual) HQA01560@niftyserve.or.jp (off time) %
(A note from the editor: Dr. T. Ishida has a handle name of "usagi" in Japanese, meaning a rabbit or a hare. Since nothing particular happens in March, he must be identified as a rabbit according to my observation.)
PS. The editor's name (Taichi) originally meant "Polaris" in ancient Chinese.
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